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Boost-regulated Timing Retard...

Looking for a box that will allow me to retard timing based on boost. I know there are boxes from SplitSecond and MSD that will do this. However, I was looking for alternatives other than these. Any help/input appreciated.

Because...

First, the MSD boxes are big and ugly. Since I'm trying to maintain some semblence of "stock" under the hood, I was hoping for something small and understated.

Second, this will be for an M70 V12 Twin Turbo which is basically two six cylinders that share a crank. Because of this, size is even more important as there will be two of everything under the hood. Space is at a premium so the MSD Boost Timing Master units have already been ruled out.

I never liked the idea of external timing control devices on ECUs. External adjustments to get the fuel right is bad enough, but adding on another layer of the timing. Ends up making the engines just feel "lumpy" since the total timing isn't smooth and linear as you build boost from a low vacuum.

Well...

Originally Posted by Def

Why not get your factory DME tuned by somebody?
I never liked the idea of external timing control devices on ECUs. External adjustments to get the fuel right is bad enough, but adding on another layer of the timing. Ends up making the engines just feel "lumpy" since the total timing isn't smooth and linear as you build boost from a low vacuum.

The reasoning is not so simple, actually. To begin, there are three separate ECU's that controll the V12 engine. There are two DME's (one for each bank of six cylinders) plus an EML that coordinates and synchronizes the actions of the two DME's. The problem lies in that the EML has several code bugs - - one of which prevents WOT operations at anything under ~4200 RPM's.

I've disassembled the EML code in hopes to correct this bug. However, in the meantime, I wanted to experiment with a couple of different piggyback units - the possibilities of which I am exploring in this thread. Once I'm finished "playing", my plan is to use the fuel/spark mods from these piggyback controllers to modify the maps within the DME's themselves - - thus eliminating the piggyback units from the equation. In short, it's a learning exercise.

Was out of the country, actually...

Originally Posted by card counter

John where have you been. How are things glad to see you posting.

Back now. Just haven't participated on the board much lately. Removed my turbo manifolds in order to have a pattern made - - this, in hopes that other 850 owners will be able to build twin turbo setups of their own. The jig/pattern should be completed in the next few weeks afterwhich I can re-assemble the car and return it to its previous daily driver status.

Still hoping to connect with some of the other DC-Area boost junkies in the near future. Rgds...

J&s

I also used a J&S box on my 535is turbo. Its an active knock sensor that reatards timing. Dinan used them for years. My J&S box saved the 535is twice..Both overboost situations. Once when the boost control failed and I got a 16psi spike. And once when the wastegate signal line came off at a track.

They work great and you can get dual sensor set ups. Not sure how it would work on a 850 since it essentially has two ecu's.